title: Effects of ascorbic acid and sugars on solubility, thermal, and mechanical properties of egg white protein gels.
abstract: The effects of reducing sugars (fructose, glucose, ribose, and arabinose), sucrose, and ascorbic acid were studied on thermo-mechanical properties and crosslinking of egg white proteins (EWP) through Maillard reaction. Sugars (0%, 1%, 5%, and 10%) and ascorbic acid (0%, 0.25%, 0.5%, and 2.5%) were added to EWP solutions. Thermal denaturation and crosslinking of EWP were characterized by differential scanning calorimetry (DSC). Mechanical properties (failure strength, failure strain and Young's modulus) of modified and unmodified EWP gels were evaluated by texture analyzer. Ascorbic acid decreased thermal denaturation temperature of EWP, but the reducing sugars increased the denaturation temperature. DSC thermograms of EWP showed that ascorbic acid exhibited an exothermic transition (≈110 °C) which was attributed to Maillard crosslinking of the protein. The reduction in pH (from 7.21 to ≈6) and protein solubility of egg white protein gel (from ≈70% to ≈10%) provides further evidence of the formation of Maillard cross-linking. Reactive sugars (ribose and arabinose) increased the mechanical properties of EWP gels, whereas ascorbic acid decreased the mechanical properties. Generally, the effect of ascorbic acid was more pronounced than that of various reducing sugars on the thermal and mechanical properties of egg white proteins.
authors.affiliation: Food Biopolymer Research Group, Department of Food Science and Technology, Islamic Azad University, Damghan Branch, Damghan, Semanan, Iran. Electronic address: fstiau@gmail.com.
authors.forename: Abdorreza
authors.initials: A
authors.lastname: Mohammadi Nafchi
authors.forename: Ramin H
authors.initials: RH
authors.lastname: Tabatabaei
authors.forename: Bita
authors.initials: B
authors.lastname: Pashania
authors.forename: Hadiseh Z
authors.initials: HZ
authors.lastname: Rajabi
authors.forename: A A
authors.initials: AA
authors.lastname: Karim
mesh_terms: D001205:Ascorbic Acid / Q000737:chemistry*; D002241:Carbohydrates / Q000737:chemistry*; D004527:Egg Proteins / Q000737:chemistry*; D005782:Gels; D006863:Hydrogen-Ion Concentration; D055595:Mechanical Phenomena; D012995:Solubility; D013696:Temperature; D013816:Thermodynamics
chemical_list: D002241:Carbohydrates; D004527:Egg Proteins; D005782:Gels; D001205:Ascorbic Acid
keywords: Crosslinking; Egg white protein; Maillard reaction